New insights into the role of endothelin-1 in radiation-associated impotence

The objectives of this work were to: (1) Determine if prostate and penile t issue levels of endothelin-1 (ET-1) are increased in a rat following pelvic irradiation, (2) Determine if an ETa receptor antagonist (BQ-123) potentia tes erectile function in these irradiated animals. Rats were divided into t hree study groups: control, 1000 cGy and 2000 cGy, The experimental groups received a single dose of radiation to the pelvic region. A time course was established to measure the effects of irradiation on prostate and penile t issue levels of endothelin-1 (ET-1)-like immunoreactivity. The effect of in tracavernous injection of BQ-123 (25 mug/30 mul) was evaluated by measuring intracavernous pressure (ICP) following cavernous nerve electrical field s timulation. In the 2000 cGy group, a significant rise in ET-1-like immunore activity tissue levels was observed at 20 days. A significant decrease in I CP was recorded in the 1000 and 2000 cGy irradiated rats compared to the co ntrol group. Only the 2000 cGy group had a significant improvement in erect ile function following BQ-123 administration, A significant improvement was observed 20 min postadministration, lasted 90 min, and was back to pre-adm inistered levels at 120 min. The conclusion made was that radiation-induced impotence in irradiated rats is associated with an increased production of ET-1, Preliminary results are suggestive that ETa receptor antagonist may be of use to reverse such radiation-induced impotence in these irradiated a nimals.